The answer to your question depends on where you are financially and what the house is like. I'm thinking this is not a colonial mansion in Moorestown, NJ. The vinyl siding gave it away. With that in mind, there is no way I would spend that much money on those particular windows. I would replace the rotted parts of the sills. This is most likely only the outer 2 inches or so, where moisture has been trapped under the ext trim. I would also replace the brickmolding (ext trim). I would then have these openings wrapped with the aluminum of your color choice, making sure that that is sealed properly, and also installed behind whatever drip cap is above. What I'm describing is not expensive work, perhaps app $200 per opening, including material. It is also not time consuming work, and fairly straight forward. I would then choose a quality replacement window with an insert installation, preserving all your interior trim. I would think you could have all this done for less than $1k per window or so. It could be argued that the technically correct way to do this right is to gut the openings and go with full frame methods, all new everything in and out. But replacement windows are called replacement windows for a reason. It is not always desirable to replace everything. For instance, if those wood windows of yours have a rope and weight balance system, then there is a large weight pocket behind the jambs. It's just not worth it to take all that apart unless you're wealthy or doing it yourself. Just get the best window you can. I suggest fiberglass framed so that you won't lose glass space. If that doesn't bother you, high end vinyl will work as well. But don't skimp on the window. If you do, you will be back in the same boat in less than 10 years. One more thing. The aluminum wrap on the outside can be bent in such a way to have a brickmold profile. This is much more professional and attractive, and shouldn't cost any extra if you have true professionals doing the work. Good luck!

Thanks for the explanation. It sounded like frame jumping was only one method of retrofitting, but I think it's a finer distinction than that. After looking around more, I think I see why people make a distinction between frame-jumped and non-frame-jumped retrofits. With very old wood windows, once you remove the stops, you're basically down to the main opening of the window (the jambs, sill, etc.). An insert can then be fit in with no significant gap. However, with sliding aluminum windows popular in the '50s and '60s (which is what we have), apparently it can be difficult to remove enough of the original aluminum pieces (rails, etc.) to get down to the actual window opening, so most of the time it is left in place and "jumped" over, resulting in a larger loss of glass area, and a gap that must be covered with extra vinyl trim and extra large stops (as East Bay 10 mentioned). With this project coming up, as I look around, I've been wondering why so many '50s-'60s era houses with new windows have very thick looking window frames, and this explains it. It kind of makes one want to go the full-frame route, especially if you want new interior trim anyway, as many '60's era houses have little or no trim to start with.

It's an old window with pulleys and weights behind the jambs. There is a space for the weights and then there seems to be another wood frame embedded in the blocks. The jambs frame the sashes and an outer frame frames the weight pockets and the jambs. It may be only this outer frame that is attached to the masonry. So you think it is possible to remove the brickmold and jambs while leaving the stool and interior molding in place, and use a full frame replacement (with a full depth jamb and not a 3 1/4 inch jamb)? The interior trim may be nailed to the outer frame and this is what would make this possible. But I am not sure how this could be anything other than a hack job. I have only found this one mention of it anywhere. Thanks for any comments!

I have a stucco home and used Marvin Ultimate Casement Windows. The installers I used are home builders with over 25 years experience and they measured the original windows about three times and order the windows including the brickmolding attached from the factory. They took the original windows out and inserted the new windows in with no harm to the stucco. They also before hand; scored the internal wood trim and remove the trim very carefully to be re-used after the new windows were installed. Worked out perfectly on all windows. I was amazed. Only very minor touch up on the internal trim needed for the 14 windows. Everything was original trim installed back! The installers were a huge premium in labor cost but well worth the cost since no repairs were called for afterwards to the home itself. Nice and clean - surgically removed and put back.